In the related art, JP 2009-107388A (Reference 1) discloses a drive apparatus for a hybrid vehicle in which an engine and a motor are connected to elements of two planetary gear mechanisms. The drive apparatus for a hybrid vehicle can synchronize rotation during the launch and the shifting of the transmission of a vehicle by controlling the motor, and does not require a torque converter.
However, in the drive apparatus for a hybrid vehicle disclosed in Reference 1, when a gear stage is a second speed stage or an eighth speed stage, the motor is locked by the brakes, and thereby the motor cannot provide the vehicle with an assist drive force. The rotation speed of the engine decreases as the gear stage is up-shifted from a second speed stage to a third speed stage, to a fourth speed stage, and to a fifth speed stage, but the rotation speed of the motor increases. For this reason, there is a problem in that in the gear stages from the second speed stage to the fifth speed stage, the torque of the motor does not increase sufficiently, and the motor cannot be of assistance to the driving of the vehicle because a speed reduction ratio decreases further as the gear stage decreases. In contrast, the rotation speed of the motor decreases as the gear stage is up-shifted from a fifth speed stage to a sixth speed stage, to a seventh speed stage, and to an eighth speed stage. As such, from the second speed stage to the fifth speed stage, the speed reduction ratio increases, and in contrast, there is a problem in that the gear ratio cannot adjust a drive force output from the motor to an appropriate level of torque because the speed reduction ratio decreases from the fifth speed stage to the eighth speed stage.